1. Field of the Invention
The present invention relates to the treatment of coronary artery disease by mechanical dilation of blockages in the coronary arteries. More particularly, the present invention relates to a method and apparatus for dilating blockage in coronary arteries wherein a catheter assembly carries a balloon to the blockage site in a patient's artery, and the balloon is expanded to uncoil a coiled ring structure having longitudinally extended struts is carried upon the balloon, and which locks to remain in an uncoiled position, holding the blockage, flap or dissection in open dilated position.
2. General Background
A common medical condition that threatens thousands of lives is caused by blockage of the coronary arteries. Medical procedures have been designed to remove the blockage in many cases so that increased blood flow travels through the previously diseased artery. Restenosis means that coronary artery blockage returns. It is though that restenosis is due to tissue growing in the inner lining of the artery as it heals. Approximately 30% of the patients undergoing PTCA will experience restenosis. Several procedures have been developed in hopes of reducing the restenosis rate. Atherectomy is a technique by which the blockage is actually removed. It is often times referred to as the roto-rooter. This technique initially demonstrated promise but it seems that it does not effect restenosis. Another technique is stent implantation. A stent is a device that is deployed in the vessel to pin back flaps and prevent elastic recoil. Early data suggest that this procedure may reduce stenosis.
The other problem with PTCA is acute occlusion. Occlusion occurs when the artery closes off completely following balloon dilatation. This problem is usually the result of one of two things. A clot can form at the PTCA site and obstruct the vessel, or a dissection can form which is basically a flap made up of the inner and middle layers of the artery. Severe dissections have been treated by long balloon inflation times in hopes of pinning up the flap, by atherectomy where by you go in and cut off the flap, and by stenting which pins up the flap mechanically.
There are several stents currently being researched in the coronary and peripheral circulation, the most well known is the Palmaz stent. It is a stainless steel tube that is prepared by cutting a series of slots in it. It is then placed on a balloon. When the balloon is inflated the tube expends to the diameter of the balloon and foreshortens the stent upon expansion.
Another stent is the Schneider or Wall stent. This is a self-expanding stent. It is similar in design to a Chinese finger cuff. When elongated its diameter is smaller. When allowed to shorten along its longitural axis its diameter increases. Following deployment in a blood vessel it is further expanded with a balloon. Various patents have issued for stents and for catheter arrangements that are directed to the problem of coronary blockage and restenosis.
U.S. Pat. No. 4,733,665, entitled "Expandable Intraluminal Graft, And Method And Apparatus For Implanting An Expandable Intraluminal Graft," issued to Julio C. Palmaz, discloses a graft that is expanded within a blood vessel by an angioplasty balloon associated with a catheter to dilate and expand the lumen of a blood vessel. The graft may be made of a wire mesh tube.
U.S. Pat. No. 5,049,131, entitled "Balloon Catheter," issued to Jacobus A. C. Deuss, discloses a balloon catheter for the widening of passages in the body, such as blood vessels. The apparatus comprises a tubular body connected at one side to the interior of a cylindrical balloon and at another side to a pump unit. The balloon can be enlarged from a first predetermined diameter to a second predetermined diameter without completely withdrawing the catheter from the body passages.
U.S. Pat. No. 5,066,298, entitled "Article And Method Of Sheathing Angioplasty Balloons," issued to Robert L. Hess, discloses a pre-compressed angioplasty balloon catheter and method of manufacture wherein the balloon portion of the catheter is wrapped for storage and for minimizing its outside diameter for purpose of insertion into the body.
U.S. Pat. No. 5,100,381, entitled "Angioplasty Catheter," issued to Matthew M. Burns, discloses an over-the-wire balloon for use in angioplasty and includes a dual lumen shaft formed by a multisection outer tube and multisection inner tube. The outer tube includes a first thin wall outer tube section which is connected to a manifold at its proximal end. The outer tube also includes a second outer tube section which is attached to the distal end of the first outer tube section and which has a greater flexibility. The inner tube has a first thin wall inner tube section which extends generally coaxially through the first outer tube section and into the interior of the second outer tube section. The inner tube also includes a second thin wall inner tube section which is attached to the distal end of the first inner tube section and extends distally beyond the distal end of the outer tube. A balloon is attached to the distal ends of the outer and inner tubes. The inner tube sections have a coating of a low friction material, such as polyimide-polytetrafluoroethylene composite, on their inner walls to facilitate movement of a guide wire through the guide wire lumen of the inner tube.
U.S. Pat. No. 5,100,429, entitled "Endovascular Stent And Delivery System," issued to Edward L. Sinofsky et al., discloses an uncured or partially cured, collagen-based material that is delivered to a selected site in a blood vessel and is crosslinked in the blood vessel by laser energy or other suitable energy to form an endovascular stent. The collagen-based material can be delivered to the blood vessel as a coating on an inflatable balloon mounted on the distal end of a catheter. The collagen-based material can also be delivered to the blood vessel in liquid form and forced through a porous balloon to form a tubular configuration. The collagen-based material is preferably crosslinked by laser radiation carried through an optical fiber to a diffusing tip located within the balloon. In another embodiment, an endovascular stent is formed by rolling a flexible sheet of biologically-compatible material onto a an outside surface of an inflatable balloon. A crosslinkable collagen-based adhesive is used to adhere overlapping portions of the sheet together in the blood vessel and can be used to attach the stent to an inside surface of the blood vessel. The collagen-based adhesive is crosslinked in the blood vessel by application of laser energy or other suitable energy. A photodegradable adhesive can be used on an inside surface of the stent to releasably attach the stent to the inflatable balloon.
U.S. Pat. No. 5,102,417, entitled "Expandable Intraluminal Graft, And Method And Apparatus For Implanting An Expandable Intraluminal Graft," issued to Julio C. Palmaz, discloses a plurality of expandable and deformable intraluminal vascular grafts that are expanded within a blood vessel by an angioplasty balloon associated with a catheter to dilate and expand the lumen of a blood vessel. The grafts may be thin-walled tubular members having a plurality of slots disposed substantially parallel to the longitudinal axis of the tubular members, and adjacent grafts are flexibly connected by at least one connector member.